In oil fields, it is very common to find oil dispersed in water. This occurs during steam flooding, water flooding or other oil recovery procedures in which the oil is mixed with water.
Dispersion also occurs in water in the vicinity of the oil well.
An oil-in-water dispersion is difficult to distinguish from an oil-in-water emulsion.
In an oil-in-water emulsion, the water contains a sufficient level of surfactants or emulsifying agents. The surfactants may either be natural occurring or man-made. Oil-wet solids also play a role in stabilizing the emulsions. The solids sterically inhibit the oil droplets from coalescing. The oil-in-water emulsion has an extremely long retention time.
In an oil-in-water dispersion, the water does not contain enough emulsifying agents to form an emulsion. The oil droplets are usually small and may contain solid particles which give them slight stability. Upon standing, the dispersed oil will rise to the top of the water layer and coalesce.
The problem of oil-in-water dispersions is a significant problem. Generally, water used during oil recovery must be sent to waste treatment facilities, retention ponds, or other water forces. It is not acceptable to return this waste water or the water dispersed therein. Because of the small size of the oil droplets, mechanical separation cannot reasonably be accomplished by merely waiting for the oil droplets to coalesce and separate from the water. Some form of intervention must occur. That intervention preferably, will result in rapid phase separation.